The Silver-washed Fritillary is a woodland butterfly whose larvae feed on violets (Viola spp.). It tolerates a greater degree of shade than other violet feeding fritillaries and its decline has generally been less severe (For further details on this species see http://www.butterfly-conservation.org/).

Status details : Status since 1976 is Rapid increase with a increase of 115%Status over the last 20 years is Rapid increase with a increase of 165%Status over the last 10 years is Stable with a increase of 37%

Log collated index plot

This chart shows the index of abundance (LCI = Log Collated Index) over time. It shows fluctuations in
populations from year to year, and is scaled so that the average index over the whole series is equal to 2
(horizontal line). For greater detail about how this index is derived, click on the green question mark above.

Trend description :This species was showing a steady increase up until 1996. In 1998 it experienced the biggest drop in numbers since the 1977 crash that followed the drought of 1976. There was no drought in 1997 and the reasons for this second big drop are not known. Since 1998 numbers have increased again and the overall trend is of significant increase. This is a butterfly that has been expanding its range north and eastwards and has now been recorded on more different transects than any other fritillary in the UK, although these are greatly condensed in the south-west.

Phenology plot

Phenology plot

This chart shows the average number of butterflies seen on transects between Arpil and October across all sites (fitted values from a Generalised Additive Model). The blue line gives average counts over the full BMS series (1976 to date) and the red line gives the average for the last year.

This map shows symbols for the mean abundance at transect sites, with the colour of the symbol reflecting the level of abundance. Means are over all years. Grey background squares are the occupied cells as shown by the Butterflies for the New Millenium over the previous ten year period.

Coverage

In total, Silver-washed Fritillary has been recorded from 405 transects in the Butterfly Monitoring Scheme. Of these, annual indices of abundance have been calculated from 420 sites, with an average index of 19 individuals per site.

For 201 of these sites, Silver-washed Fritillary has been recorded well enough to calculate annual indices of abundance in more years, allowing trends to be calculated.

In 2017, 11768 individuals were recorded from 220 sites, producing annual indices at 180 of these.

This map shows the trend in abundance at particular transect sites for which data has been received within the last five years. Trends (increasing, declining or stable) are assessed at sites where the species has more than five years of annual index data. Use the option boxes below to view plots for individual sites.